Laffer curve  a graph of tax revenue as a
function of tax rate, illustrating the theory that beyond a certain point,
higher rates will reduce the tax revenue received (by discouraging economic
growth).

lagniappe  a gratuity given to a
customer; a small gift

lahar  an mud-flow "avalanche" of volcanic ash and
water, down the slopes of a volcano

lallation  a speech disorder involving faulty
pronunciation or excessive use of the l-sound.

Lamarckism  eponym: theory that one passes his acquired physical traits
to his descendants

lambada  a fast, rhythmical, erotic dance, from Brazil,
with close physical contact (also, the music used)

lambdacism  faulty pronunciation or
excessive use of the l-sound (underuse of it is paralambdacism; see entry at rhotacism)

lampadomancy  divination by candles and lamps [dictionary at mancy lists 54 form of
divination]

lectica  a kind of litter or
portable couch used by the ancient Romans

leeftail  in great demand; having a
quick sale

leer  to look (at) with
a sly, immodest, or evil expression (noun: the look itself)

left and right, in politics  [from a reader]
after the French Revolution, the nobles in the French National Assembly were
seated on the president's right and the Third Estate was seated on the
president's left. The sides were referred to as left and right (in French); Great Britain borrowed this terminology, and the
US then took it from Great Britain
 though neither of those countries ever used the French seating arrangement.

leonine of or like a lion [Also, Leonine verse (eponym)  verse in which a word in the middle of a line rhymes
with a word at the end. This is a separate word, from Leonius, 12th-century canon of the church of St. Victor,
in Paris, who used this form.

leporine  hare-like

lethologica  forgetfulness of words; inability to recall right word

lettre de cachet  a warrant issued for the imprisonment of a person without
trial, at the pleasure of the monarch

liffy  to seduce a woman with promises of fidelity, and then desert her

ligature  a character, such as ζ, combining two or more letters; something
that ties or binds

light year  1.astronomical:
a certain huge measure of distance, used in measuring interstellar space. It is
the distance light travels in a year. 2.metaphoric:
a very large distance or figurative distance

lithography  printing with a
plate whose areas are chemically treated to retain or repel ink

lithomancy  divination by stones [dictionary at mancy lists 54 form of divination]

litmus test  a test that relies on a single
indicator ("Her litmus test for good breeding is whether you split
infinitives.")

litotes  rhetoric: a
deliberate, modest understatement (typically meant to imply the opposite): I
have this tiny little tumor on the brain (compare meiosis). One form is to negate the contrary: He is no fool.

lothario; Lothario  eponym: a seducer of
women; a libertine; a lady-killer

lotus eater  a lazy person devoted to pleasure and luxury. lotus land  a place or state of
languid contentment. (Wordcrafter's note: in my
judgment they connote a sense of drugged unreality, which the dictionaries have
missed.)

louche  disreputable or dubious; shady  but in a rakishly
appealing way

luferlang  mythical creature that can run
in either direction; easily identified by the tail in the middle of its back.
It bite is almost certain death; the biting season usually occurs on July 12.
Avoid green clothing, which tends to arouse the creature further; conversely, a
conspicuous orange-colored handkerchief will invariably afford full protection.
Or, since the luferlang is terribly frightened of
seeing itself, carry a big mirror so that in the event of luferlang
attack you can hold that mirror in front of you.

luftmensch  an impractical dreamer,
without business or income

Luger  eponym:
semiautomatic pistol widely used by Germans in WWII (though introduced
earlier). Some consider it to be the finest pistol ever produced.

maggotorium  a place where maggots are bred for use as
bait by anglers

maggotry
foolishness, absurdity. Obsolete

Maginot line(also here) eponym: an expensive defense that seems
impregnable, creates a false sense of security, but proves utterly ineffective
(typically because it is static and thus cannot respond to other means of
attack).

maieutic  a technique in
which a teacher (rather than giving information) asks a series of questions to draw
out, from the student, ideas previously latent in the students mind [A more
common word for this is Socratic (eponym). A few sources also give hebamic as a rare word of the same meaning.]

mail slot  a slot or slit in a door (occasionally in a wall),
through which mail can be delivered

Main Street  typical, average Americans (or,
typical small-town Americans), taken as a group. [Note: a derogatory sense of
"parochial, conservative" is common in the dictionaries but much less
common in usage.]

maintenance ­ law: an outsider unjustifiably stepping in to
assist a litigant

maisonette  Brit: a two-floor apartment in a larger building, often with
its own entrance

malleable  easily controlled
or influenced; tractable (also, able to adjust to changing
circumstances; adaptable). In science, a malleable metal is one that can
be hammered or pounded into thin sheets; contrast ductile

malt  grain (usually
barley) that has been sprouted (to convert the seeds starch into sugar) and
then dried. The first step in brewing.

malversation corruption by one
in public office or a position of trust.

malware  malicious software, designed to damage or disrupt a
system [see virus; Trojan; worm]

mamihlapinatapei(foreign)  a shared glance of longing between
two people, each knowing the meaning and each wishing the other will initiate
something where neither is quite willing to make the move. [from
the Fuegian language of Tierra
del Fuego]

manciple  a person
responsible for provisioning a group of people (more specifically, one
who purchases provisions for a college, monastery, Inn of Court, etc.)

mancy  suffix meaning divination; foretelling the future. Divination
forms include divination by the air:aero-;cocks:alectro-;meal, flour, or bran:alphito-;human entrails:antinopo-;numbers:arith-;dice:astragalo-;flight or entrails of birds:augery;saws:axino-;herbs:botano-;asses' heads:cephaleono-;writing in papers, and Valentines:charto-;the hands:chiro-;crystals:crystallo-;rings:dactylo-;devils and evil spirits:demono-;sound of or marks upon the belly:gastro-;earth:geo-;circles:gyro-;water:hydro-;fishes:icthyo-;idols, images, and figures:idolo-;vessels of brass or other metal:kaltabo-;smoke:kapno-;looking-glasses:katoxtro-;the melting of wax:kero-;lots:klero-;sieves:koseino-;corn or grain:kritho-;candles and lamps:lampado-;basins of water:lecano-;stones:litho-;burning of incense:livano-;logarithms:logarith-;knives and swords:macharo-;summoning the dead:necro-;lees of wine:oino-;the navel:omphelo-;the nails:onchyo-;dreams:oneiro-;names:ono-;birds:ornitho-;feet:podo-;soul, affections, or dispositions of men:psycho-;fire:pyro-;stars:roado-;shadows:scio-;skins, bones, &c:spatala-;the elements:stareo-;marks from the breast to the belly:sterno-;figs:syco-;ashes:tephro-;Scriptures, or word of God:theo-;beasts:therio-;cheese:tyro-

mentor  eponym: a wise and
trusted counselor or teacher; also, v.tr.andv.intr.to serve as such a counselor or teacher, esp. in a
job-setting. (1750, from Mentor,
character in the Odyssey, who was
often actually Athene in disguise)

mestizo  either a person of mixed ancestry (say some dictionaries) or
specifically european/american-indian mix (say other
dictionaries). see also mulatto

metallised (or metalled) road  a road that has been tarmacked

metamorphosis  a complete change in physical nature, as if by magic; also,
striking change in appearance or character (the metamorphosis of the old
house); also, the change in certain animals (e.g., a butterfly) from larva to
adult. metamorphic
 relating to metamorphosis, particularly of rocks

metanalysis  creation of a new word by reinterpreting the form of an old
one

meteor  the streak of
light as a stone passes through the earth's atmosphere; also, the stone
itself during that passagemeteoroid  a stone in
interplanetary space, too small to be an asteroidmeteorite  the stone,
formerly a meteor, after having come to rest on or in the earthmeteoric  of very sudden brilliance, swiftly rising and seemingly
coming from nowhere.

metheglin  a drink of
fermented honey and water (also called mead), esp. when spiced or
medicated

Methuselah  eponym:a very old man. (by extension:1.
any plant or animal alive but extremely old for its kind or circumstances 2.
pertaining to extremely long life-span.) Also: a certain large
wine-bottle

metonymy  substituting one
word or phrase for another with which it is closely associated, as Washington for the United States government.metonym

mithridatism
(eponym) 
tolerance or immunity to a poison, acquired by taking gradually larger doses of
it.mithridate
an antidote against poison, especially a confection formerly held to be an
antidote to all poisons.

moon-calf  originally: a misshapen mass in the uterus (thought to be caused by the
baleful influence of the moon); a false pregnancy; also, from this: a
monstermore commonly: a born fool; a simpleton; or one given to
absent-minded daydreaming (but coming to be used in the sense of
"someone sentimentally love-sick")

mooreeffoc  the queerness of things which,
previously trite, are suddenly seen from a new angle

moot  1.subject to debate; arguable.2.law: of no practical importance in the
context of the case; irrelevant

moraine  a mass of rocks
and sediment carried down and deposited by a glacier

morganatic  of or pertaining to a legal
marriage between a person of royal or noble birth and a partner of lower rank,
in which no titles or estates of the royal or noble partner are to be shared by
the partner of inferior rank nor by any of the offspring of the marriage.

morpheme  a unit of meaning that cannot be broken down into smaller such
units. (It can have one or more syllables but isn't necessarilly
a complete word.) A free morpheme can stand
alone; a bound morpheme must combine with a
free morpheme, which it modifies. Thus the word attempting contains a free morpheme (attempt) and a bound morpheme ( -ing).

Mortons Fork  eponym: the principle that "youre
damned if you do, and damned if you dont"

mossback  a very old-fashioned person, one
with ancient views or thinking; an old fogy

motjuste (French)  the precisely
right word or
expression

mother-in-law  Old and Bitter; that is, a mixture of Old Ale (heavy beer more
commonly drunk in the winter) and Bitter (the most common type of English beer,
usually quite hoppy in flavor)

motile  Biology: having the power to move spontaneously

mottle  verb: to mark with splotches or blots. noun:
such a splotch or blotch; also, a variegated pattern, as on marble

Munchausen syndrome  psychological disorder in which one
repeatedly seeks medical attention for physical symptoms  knowing that he is
fabricating or exaggerating the symptoms, or that they are self-inflicted

munchkin  eponym: a very small
person, often endearing; a child; a minor official

mundungus  foul-smelling tobacco (also, apparently
slang, in the Royal navy, for any useless or unwanted material, like gubbins, wiffen, etc.)

munge  to imperfectly transform information

Munich  toponym: shortsighted and often dishonorable appeasement of a tyrant

munificent  very liberal in giving or
bestowing; very generous; lavish

munition; munitions  war material of any kind
(weapons, equipment, stores, etc.), but especially weapons. (verb:
to supply with munitions) Especially weapons, but not
necessarily firearms. OED quotes show the term used for items from
spears and pikes to atomic bombs.

Murphy game  eponym: any of various
confidence games often having the services of a prostitute as a lure

Murphys Law  eponym?: if
anything can go wrong, it will [No one is sure who Murphy was.]

murrain  originally, a pestilence or
plague; now particularly a plague among domestic animals

murrey  dark red; dark purplish red. (frommulberry)

muscatel (etymology)  Italian for "wine
with flies in it"

musjid  see masjid

musth  (of a male animal, esp.
an elephant or camel:) in heightened
aggression and unpredictable behavior, usually occurring annually in
association with a testosterone surge (also
noun: the such condition)

mutable  prone to change; inconstant; also, capable of
change or of being changed (antonym: immutable)

mutatis mutandis  (when comparing two or more cases) making
necessary alterations while not affecting the main point; with respective
differences taken into consideration

Mutt and Jeff  eponym:a
pair of comically mismatched people, esp. one tall and one short; also,
a pair of lovable losers

muumuu  a long dress,
loose and unbelted, hanging free from the shoulders